Condition responsive device



Aug. 16, 1960 R. w. BARTHEL CONDITION RESPONSIVE DEVICE Filed May 2 9elm-2% m m m m ROY w. BARTHEL United States Patent Ofifice 2,949,514Patented Aug. 16, 1960 apolis-Honeywell Regulator Company, Minneapolis,Minn., a corporation of Delaware Filed May 25, 1959, Ser. No. 815,693

5 Claims. (Cl. 200-61-06) The present invention is concerned with animproved humidity responsive device; in particular, the device has ameans for providing a constant strain release for the responsiveelement.

Where a moisture responsive element such as a human hair element is usedfor control or indicating purposes, the reliability of the elementdepends greatly upon the type of physical forces which are applied tothe element. Since such elements are generally under tension, a means isoften provided to prevent the tension from exceeding a destructivelimit. The element might be connected at one end to a movable supportwhich is biased by a strain release spring; however, the physical sizeof the instru-,

merit can limit the type of strain release spring used.

In the present invention a strain release means is rovided for limitingthe maximum tension which can be applied through a moisture responsiveelement. The strain release means is maintained substantially constantthroughout the calibration range of the device.

An object of the present invention is to provide an improved conditionresponsive device.

Another object of the present invention is to provide an improvedcondition responsive device which has a means for providing asubstantially constant strain release on the condition responsive means.

These and other objects will become apparent upon the study of thefollowing specification and drawings of which:

Figure 1 is a front view of the humidity responsive device with thecover and control point adjustment knob removed.

Figure 2 is a side sectional view of the device of Figure 1 with theportion of the cover and the control point adjustment knob shown.

Referring to Figures 1 and 2, a base is shown. The base is adapted to bemounted on a wall or surface to cover a hole for housing an associatedactuator or switch 11. A rotatable shaft 12 is pivotally supported on apin 13 projecting outward from the center of base 10. A control pointadjustment knob 14 is connected as an integral part of shaft 12. A cover*15 for the unit has an opening for receiving the control pointadjustment knob 14. The cover is held onto the base by a pair of screws20, only one of which is shown in Figure 2. Around the outer peripheryof cover 15, a shielded grill 21 provides an opening for the transfer ofmoisture to and from the space inside the cover. Switch '11 is of aconventional snap switch type having an operating button 22 which ismoved by a pivoted lever 23 having a portion 24 projecting to the frontof base -10.

A condition or moisture responsive element 30 is of the human hair typewhich changes in length as the moisture in the air surrounding theelement changes. A cam rider or lever 31 is pivotally mounted on a post32 projecting from base 10. Element 30 is connected at its extremitiesbetween a projecting arm 33 of rider 31 and portion 24 of the switchoperating lever. The element is looped over a tension equalizer 34 whichis 2 made up of a yoke 35 pivotally supported upon a member- 40. Thetension equalizer provides for two portions of the element 30 which havean equal tension.

A cam 41 is attached to shaft 12. The cam is characterized to providecalibration of the device when the position of the cam is adjustedbetween the limits established upon lever 72 engaging stops 70 and 71.Cam rider 31 is biased in a clockwise direction by a spring 42; so that,a foot 43 of the cam rider engages a surface of cam 41. Upon rotation ofthe control point adjustment knob 14, card rider 31 is adjusted tochange the position of arm 33 and thus one extremity of element 30 toselect a change of length of the element which is necessary to operateswitch 11.

While the control point adjustment is done by the positioning of cam 41,a factory calibration is accomplished by re-positioning member 40 aboutone end 50 which is pivotally attached to base 10. A screw 51 isattached to the base by means of a ball and socket connection 52, andthe other extremity of the screw is threaded into member 40. By rotatingscrew 51, the position of the tension equalizer 34 is changed torecalibrate the length of element 30 necessary to operate the switch. I

A second cam rider or lever 60 is pivotally supported about a post 61projecting from base 10. Cam rider 60 has an arm 62 to which spring 42is connected. A foot 63 of cam rider 60 is biased against the surface ofcam 41 'by a spring 66. When cam 41 is rotated, the relative positionsof cam riders 31 and 60 are adjusted to maintain the distance betweenthe extremities of the spring, or the spring length, substantiallyconstant.

If a long spring is used for strain release spring 42, any change in theposition of cam rider 31 with the other end of the spring fixed hasrelatively little affect upon the change in tension of the spring. Inthe particular application, the inventor was required to keep the sizeof the device at a minimum. To use a short spring such as 42, thetension of the spring changes appreciably as the length of the springchanges. By moving both ends of the spring together, when the controlpoint adjustment knob 14 is rotated, a substantially constant strainrelease is provided for element 30'.

The operation of the condition responsive device" is as follows. Whenlever 24 moves to a certain position to push in operating button 22,switch 11 is operated. Whether the switch operates to close a circuit oropen a circuit is a matter of choice and depends upon the type ofapparatus to be controlled. During factory calibration, screw 51 isadjusted; so that, when the moisture content of element 30 is at apredetermined value, the switch 11 will operate if control pointadjustment knob 14 is turned past the selected position. Aftercalibration, screw 51 is sealed.

Upon the rotation of knob 14 to a predetermined position selecting adesired moisture level as indicated by an appropriate scale (not shown),cam 41 is rotated to change the position of cam rider 31 and thus theone end of element 30 connected to aim 33. When the moisture content ofelement 30 increases beyond the selected level, the element will expandto move lever 23 in a clockwise direction as shown in Figure 2 tooperate switch 22. As lever 31 moves, one end of spring 42 is readjustedwhich would normally change the tension of spring 42; however, sincelever 60 is also re-adjusted by cam 41, spring 42 is maintained at alength constant.

Let us assume that the humidity affecting element 30 decreases to such alevel that element 30 is shortened to lift foot 43 ofi of cam 41. Themovement of lever 31 provides the strain release to prevent damage tothe element which might stretch beyond its elastic limit if the endattached to arm 33 were fixed. Since the length of spring 42 ismaintained substantially constant, the strain release is substantiallyconstant. The substantially constant strain release can be provided bya. short spring 42 since the position of lever 33 does not affect thelength of thespring.

The present invention has been described in connection with a moistureresponsive device; however, the invention should not be limited to theone particular use, but the scope of the invention should be limitedonly by the appended claims.

I claim 1. In a humidity control device, a round shaped base, a switchmounted on the back side of said base, said switch having an operatinglever protruding through said base to the front of said base, a cam, ashaft rotatably mounted at the center of said base and extendingperpendicular to the front of said base, an adjustment knob attached tothe end of said shaft, said cam being. attached to said shaft, a firstcam rider pivotally mounted on said base, a humidity responsive elementbeing long with respect to its cross sectional dimensions, said camrider having a first projecting arm, means connecting said responsiveelement between said operating lever and said arm so that upon a changein the length of said element as the humidity changes said switch isactuated, said cam rider determining the position of one end of saidresponsive element whereby the control point of said switch can beadjusted by said knob, a second cam rider pivotally mounted on said baseand having a second projecting arm, a bias spring, said first cam riderhaving a third arm, means connecting said spring between said second armand said third arm for providing a strain release for said responsiveelement whereby upon rotation of said knob to adjust the position ofsaid first arm and the control point, said second cam rider is adjustedto maintain said spring at a constant tension, and a cup-shaped covermounted on said base, said cover having an opening for said knob.

2. In a humidity control device, a base, actuator means, said actuatormeans being mounted on said base, said actuator means being adapted tocontrol humidity changing apparatus, an adjustable cam, a first camrider, a humidity responsive element changing in length as the moisturecontent of the surrounding air changes, means connecting said elementbetween said actuator and said cam rider whereby the position of saidrider on said cam is effective to determine the control point of saidactuator, a second cam rider engaging said cam at different positionthan said first rider, and a strain release spring connected 4 betweensaid first and said second cam riders whereby upon the tension of saidelement exceeding a predetermined value said first cam rider is liftedoff of said cam, said spring being maintained at a constant length andthus a constant tension when the control point is changed by moving saidcam.

3. In a device responding to the condition, a condition responsiveelement having a length indicative of a condition, first means to bepositioned, a pivotally mounted lever, an adjustable stop, said stopsupporting said lever, means connecting said element between said leverand said first means whereby a change in the length of said element isetfective to position said first means, said lever being eifective upona change in position to change the control point of said element, asecond pivotally mounted lever, a strain release resilient meansconnected between said first and second levers for holding said firstlever on said stop, said first lever being free from said stop when atension in said element exceeds said strain release, and means foradjusting the position of said stop and a position of said second levelalong a predetermined relationship to vary the calibration of saidelement and to maintain a constant strain release.

4. In a condition responsive device, a condition responsive elementchanging in length as a condition changes, means connected to respond toa change in length of said element, said means being connected to oneextremity of said element, a calibration level attached to anotherextremity of said element whereby the eifect of the length of saidelement on said first mentioned means can be selected, a strain releasemeans, means connecting said release means to said lever, and means foradjustingsaid strain release means as said calibration level isadjusted.

5. In a condition responsive device, a condition responsive elementchanging in position as a condition changes, means connected to respondto a change in position of said element, said means being connected tosaid element, a calibration lever attached to said element whereby theeffect of the position of said element on said first mentioned means canbe selected, a strain release means, means connecting said release meansto said lever, and means for adjusting said means as said calibrationlevel is adjusted to maintain said strain release substan tiallyconstant.

No reference cited.

